The present invention relates to film-developing tanks. More particularly, this invention concerns the color film developing tanks.
It is known in the art of film-developing tanks to provide a tank with a removable cover to close the corresponding opening of the tank. This opening is designed to introduce therethrough into the interior of the tank a film to be developed and a developing liquid.
The tank usually includes a lower part, that is a base, and a removable upper part, that is a removable cap, which is to be installed (i.e., threaded) on the lower part after the film to be developed is inserted in the same.
The cover is designed to be removably installed on the upper part of the tank. Thus, by taking off the cover one can very quickly and easily fill or empty the tank with the developing liquid without withdrawing every time the upper part of the tank itself. Besides that, even with the withdrawn cover of the tank the film can safely remain in the tank without being spoiled by an inadvertent exposure. In order to insure this, the upper part is provided with a labyrinth sealing arrangement which overlaps the corresponding opening of the tank thus preventing any undesired light penetration in the interior of the tank in general, and onto the developing film reel in particular.
During the developing process gas is likely to evolve (particularly, when a color film is developed) in the interior of the tank. The pressure of the gas acts against the walls of the container, including the cover, thus tending to undesirably dislodge the latter from the tank. Should it be the case, then the developing liquid may splash out the tank resulting in undesired consequences, such as for example fouling of the laboratory devices. Besides that, the amount of the developing liquid inside the tank decreases correspondingly by the amount of the liquid left in the tank, thus making the developing mistakes very likely to occur.
It is a common practice in order to compensate for the unavoidable gas pressure from inside the tank to open the cover from time to time during the developing process to relieve the gas pressure from the interior of the tank.
It is to be mentioned, however, that since a present developing process includes a number of such developing baths, it is a very cumbersome taks on part of the operator to accomplish such a manual degassing of the film-developing tanks during the developing process.